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Lapatinib ditosylate (Tykerb) - Uses, Dose, Side effects,

Lapatinib is a targeted therapy used in the treatment of certain types of breast cancer. It specifically targets and inhibits the HER2 (human epidermal growth factor receptor 2) protein and the epidermal growth factor receptor (EGFR) on the surface of cancer cells. Overexpression or amplification of the HER2 gene can promote the aggressive growth of cancer cells. Not all breast cancers have high HER2 levels, but for those that do, treatments like lapatinib can be effective.

Lapatinib (Tykerb) is a dual kinase inhibitor that is available as an oral medicine for the treatment of patients with breast cancer. It exerts its action by inhibiting the HER2/neu and epidermal growth factor receptor pathways.

Lapatinib (Tykerb) Uses:

Breast cancer:
- Treatment of human epidermal growth receptor type 2 (HER2) overexpressing advanced or metastatic breast cancer (in combination with capecitabine) in patients who have received prior therapy (with an anthracycline, a taxane, and trastuzumab)
- HER2 overexpressing hormone receptor-positive metastatic breast cancer in postmenopausal women where hormone therapy is indicated (in combination with letrozole)
- Limitations of use:
  - Patients should have disease progression on trastuzumab prior to initiation of treatment with lapatinib in combination with capecitabine.
Off Label Use of Lapatinib in Adults:
- HER2 overexpressing metastatic breast cancer (in combination with trastuzumab) with progression on prior trastuzumab-containing therapy
- HER2 overexpressing metastatic breast cancer with brain metastases (in combination with capecitabine)

Lapatinib (Tykerb) Dose in Adults:

Lapatinib (Tykerb) Dose in the treatment of metastatic, HER2+ Breast cancer (with a prior anthracycline, taxane, and trastuzumab therapy):

Lapatinib is a medicine used for a certain type of advanced breast cancer called HER2+.
If someone has already had specific other treatments (like anthracycline, taxane, and trastuzumab) and they still have cancer, they might take Lapatinib.
The dose is 1,250 mg, taken by mouth once a day.
They will also take another medicine called capecitabine.
They keep taking these medicines until the cancer gets worse or the side effects are too much

Lapatinib (Tykerb) Dose in the treatment of metastatic, HER2+ Breast cancer (hormonal therapy indicated):

Lapatinib is used for advanced HER2+ breast cancer.
When someone needs hormone treatment for this cancer, they can take 1,500 mg of Lapatinib by mouth every day.
They also take another medicine called letrozole.
They continue these medicines until the cancer gets worse.

Lapatinib (Tykerb) Dose when used as a first-line therapy metastatic, HER2+ Breast cancer with brain metastases (off-label):

For people with advanced HER2+ breast cancer that has spread to the brain, Lapatinib might be used as a first treatment option, even if it's not the usual recommendation.
They'd take 1,250 mg of Lapatinib by mouth every day, along with another medicine called capecitabine.
They'd keep taking these until the cancer gets worse or the side effects are too harsh.

Lapatinib (Tykerb) dose in the treatment of metastatic, HER2+ Breast cancer with progression on prior trastuzumab therapy (off label):

Lapatinib Dosage for a Specific Breast Cancer Case:

If someone with advanced HER2+ breast cancer got worse after taking a medicine called trastuzumab, they might take Lapatinib as an alternative treatment (even if it's not the standard choice).
They would take 1,000 mg of Lapatinib by mouth every day, together with trastuzumab.

If You Forget a Dose:

If someone forgets to take their Lapatinib dose one day, they should just take their regular dose the next day. They shouldn't take double the amount.

Lapatinib (Tykerb) Dosage adjustment for concomitant CYP3A4 inhibitors/ inducers:

If Taking Other Medicines that Affect Lapatinib:

Some drugs can interfere with how Lapatinib works because they affect an enzyme called CYP3A4. So, adjustments might be needed:
- For medicines that increase CYP3A4 activity (CYP3A4 inhibitors):
  - It's best not to take them with Lapatinib.
  - If they have to be taken together, the Lapatinib dose might be reduced to 500 mg daily, and the person should be watched closely for any side effects.
  - If the CYP3A4-increasing medicine is stopped, wait about a week before going back to the regular Lapatinib dose.
- For medicines that decrease CYP3A4 activity (CYP3A4 inducers):
  - Again, it's best not to take them with Lapatinib.
  - If they have to be taken together, the dose of Lapatinib might be increased slowly, based on how well it's tolerated and up to certain maximum amounts:
    - With capecitabine, up to 4,500 mg daily.
    - With letrozole, up to 5,500 mg daily.
  - If the CYP3A4-decreasing medicine is stopped, then go back to the regular Lapatinib dose.

Use in Children:

Not indicated.

Lapatinib Pregnancy Risk Category: D

Lapatinib, a drug used in cancer treatment, might harm an unborn baby based on how it works and animal studies. Therefore:

Pregnant women should know about the risk to their baby.
Women who could become pregnant should also be aware of this risk.
A major medical group, the European Society for Medical Oncology (or ESMO for short), suggests waiting to take medicines like Lapatinib until after the baby is born if the patient has a certain kind of cancer (HER-2 positive).
Before starting Lapatinib, doctors should check if a woman is pregnant.
Women who can get pregnant, and men with partners who can get pregnant, should use safe birth control methods while taking Lapatinib and for 1 week after the last dose.

Use of lapatinib during lactation

We don't know if Lapatinib gets into breast milk.
But because it might harm a baby who is breastfeeding, women taking Lapatinib should not breastfeed while on the medicine and for 1 week after the last dose.

Lapatinib (Tykerb) Dose in Kidney Disease:

No dosage adjustments provided in the manufacturer’s labeling (has not been studied).
However, due to minimal renal elimination (<2%), dosage adjustments may not be necessary.

Lapatinib (Tykerb) Dose in Liver disease:

Mild or Moderate Liver Issues (Class A or B):

The label doesn't suggest changing the Lapatinib dose.

Severe Liver Issues (Class C):

Adjustments are suggested for severe liver problems, but there's no direct proof from clinical studies.
If taking Lapatinib with capecitabine, lower the dose from 1,250 mg to 750 mg once a day.
If taking Lapatinib with letrozole, lower the dose from 1,500 mg to 1,000 mg once a day.

If Severe Liver Problems Happen During Treatment:

Stop taking Lapatinib completely if severe liver problems occur during treatment. Don't start it again (no rechallenge).

Common Side Effects of Lapatinib (Tykerb):

Central Nervous System:
- Fatigue
- Headache
Dermatologic:
- Palmar-Plantar Erythrodysesthesia
- Skin Rash
- Alopecia
- Xeroderma
- Pruritus
- Nail Disease
Gastrointestinal:
- Diarrhea
- Nausea
- Vomiting
- Mucositis
- Stomatitis
- Anorexia
- Dyspepsia
Hematologic & Oncologic:
- Decreased Hemoglobin
- Decreased Neutrophils
- Decreased Platelet Count
Hepatic:
- Increased Serum Aspartate Aminotransferase
- Increased Serum Alanine Aminotransferase
- Increased Serum Bilirubin
Neuromuscular & Skeletal:
- Asthenia
- Limb Pain
- Back Pain
Respiratory:
- Dyspnea
- Epistaxis

Less Common Side Effects of Lapatinib (Tykerb):

Cardiovascular:
- Decreased left ventricular ejection fraction
Central nervous system:
- Insomnia

Contraindications to Lapatinib (Tykerb):

If someone is very allergic to Lapatinib or any part of the medicine, they shouldn't take it.

Warnings and precautions

Heart Issues with Lapatinib:

Lapatinib might lower the heart's ability to pump blood, known as left ventricular ejection fraction (LVEF), especially in the first 3 months of taking it.
Before starting and during treatment, heart tests should be done to check the LVEF.
If there's a significant drop in LVEF or it goes below a certain level, stop taking Lapatinib. If the heart function improves after 2 weeks and there are no symptoms, a lower dose might be restarted.
Be extra careful with Lapatinib if someone has conditions that might affect heart function or has a history of heart issues. This includes those who've had specific treatments like anthracyclines or chest radiation.
The American Heart Association warns that Lapatinib might either directly affect the heart or make existing heart issues worse.

Skin Issues with Lapatinib:

Some people have had severe skin reactions while using Lapatinib.
If someone develops a serious skin problem, like a rash with blisters or sores in the mouth, or conditions known as erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis, they should stop taking Lapatinib.

Dealing with Diarrhea while Taking Lapatinib:

Diarrhea is quite common when using Lapatinib, usually starting within 6 days and lasting around 4 to 5 days.
It can sometimes be severe and even dangerous.
The key is to act quickly: if someone notices changes in their bowel movements, they should tell their doctor right away.
If diarrhea starts, even with the first loose stool, they can use medicines to stop it (antidiarrheal agents).
If diarrhea gets really bad, they might need extra fluids, minerals, antibiotics (if it lasts more than 24 hours, has fever, or low white blood cell count), and even a pause in Lapatinib treatment, dose reduction, or stopping it altogether.

Liver Issues with Lapatinib (Warning):

There's a serious warning for Lapatinib because it can hurt the liver. Some people have had dangerously high liver enzyme levels and bilirubin levels.
These liver problems can start just days after beginning the medication or even after several months.
It's important to regularly check liver health. Tests for liver enzymes and other markers should be done before starting the medicine and then every 4 to 6 weeks, or more often if needed.
If someone has serious liver problems while on Lapatinib, they should stop the medicine and not start it again.

Lung Issues with Lapatinib:

Some people taking Lapatinib, either alone or with other drugs, have experienced lung problems like interstitial lung disease (ILD) and inflammation of the lungs (pneumonitis).
Be on the lookout for lung symptoms which might point to these conditions, like trouble breathing or a persistent dry cough.
If someone has severe lung symptoms, they should stop taking Lapatinib.

Heart Rhythm and Lapatinib:

Lapatinib can cause changes in the heart's rhythm, specifically making a part of the heartbeat (called the QT interval) longer. This can be risky.
People who already have heart rhythm problems or are on medicines that affect the QT interval should be careful when taking Lapatinib.
It's a good idea to get a heart test (12-lead ECG) before starting the medicine and at times during treatment.
Before and during taking Lapatinib, make sure levels of certain minerals in the body (like potassium, calcium, and magnesium) are right.
Taking other drugs that can also affect the QT interval with Lapatinib might raise the risk of dangerous heart rhythms.

Lapatinib and Liver Problems:

If someone has liver issues, they should be careful when taking Lapatinib.
For those with severe liver problems (classed as Child-Pugh C), a lower dose of Lapatinib might be needed.

Lapatinib: Drug Interaction

Risk Factor C (Monitor therapy)
Aprepitant	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
ARIPiprazole	CYP3A4 Inhibitors (Weak) may increase the serum concentration of ARIPiprazole. Management: Monitor for increased aripiprazole pharmacologic effects. Aripiprazole dose adjustments may or may not be required based on concomitant therapy and/or indication. Consult full interaction monograph for specific recommendations.
Bosentan	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Brentuximab Vedotin	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Brentuximab Vedotin. Specifically, concentrations of the active monomethyl auristatin E (MMAE) component may be increased.
Celiprolol	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Celiprolol.
Clofazimine	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
CYP3A4 Inducers (Moderate)	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
CYP3A4 Inhibitors (Moderate)	May decrease the metabolism of CYP3A4 Substrates (High risk with Inhibitors).
Deferasirox	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Dofetilide	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Dofetilide.
Duvelisib	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Erdafitinib	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Erdafitinib	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Erdafitinib	May increase the serum concentration of P-glycoprotein/ABCB1 Substrates.
Everolimus	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Everolimus.
Flibanserin	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Flibanserin.
Fosaprepitant	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Fosnetupitant	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Haloperidol	QT-prolonging Agents (Indeterminate Risk - Caution) may enhance the QTcprolonging effect of Haloperidol.
Ivosidenib	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Larotrectinib	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Larotrectinib	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Larotrectinib.
Naldemedine	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Naldemedine.
Naloxegol	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Naloxegol.
Netupitant	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
NiMODipine	CYP3A4 Inhibitors (Weak) may increase the serum concentration of NiMODipine.
Palbociclib	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
P-glycoprotein/ABCB1 Inhibitors	May increase the serum concentration of Pglycoprotein/ABCB1 Substrates. P-glycoprotein inhibitors may also enhance the distribution of pglycoprotein substrates to specific cells/tissues/organs where p-glycoprotein is present in large amounts (e.g., brain, T-lymphocytes, testes, etc.).
P-glycoprotein/ABCB1 Substrates	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of P-glycoprotein/ABCB1 Substrates. P-glycoprotein inhibitors may also enhance the distribution of p-glycoprotein substrates to specific cells/tissues/organs where p-glycoprotein is present in large amounts (e.g., brain, T-lymphocytes, testes, etc.). Exceptions: Loperamide.
Prucalopride	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Prucalopride.
QT-prolonging Agents (Highest Risk)	QT-prolonging Agents (Indeterminate Risk - Caution) may enhance the QTc-prolonging effect of QT-prolonging Agents (Highest Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.
Ranolazine	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Ranolazine.
Ranolazine	May increase the serum concentration of P-glycoprotein/ABCB1 Substrates.
RifAXIMin	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of RifAXIMin.
Sarilumab	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Silodosin	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Silodosin.
Siltuximab	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Simeprevir	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Talazoparib	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Talazoparib. Management: These listed exceptions are discussed in detail in separate interaction monographs.
Talazoparib	BCRP/ABCG2 Inhibitors may increase the serum concentration of Talazoparib.
Tegaserod	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Tegaserod.
Tocilizumab	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers).
Risk Factor D (Consider therapy modification)
Afatinib	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Afatinib. Management: Reduce afatinib by 10 mg if not tolerated. Some non-US labeling recommends avoiding combination if possible. If used, administer the P-gp inhibitor simultaneously with or after the dose of afatinib.
Alpelisib	BCRP/ABCG2 Inhibitors may increase the serum concentration of Alpelisib. Management: Avoid coadministration of BCRP/ABCG2 inhibitors and alpelisib due to the potential for increased alpelisib concentrations and toxicities. If coadministration cannot be avoided, closely monitor for increased alpelisib adverse reactions.
Betrixaban	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Betrixaban. Management: Decrease the adult betrixaban dose to an initial single dose of 80 mg followed by 40 mg once daily if combined with a P-glycoprotein inhibitor.
Bilastine	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Bilastine. Management: Consider alternatives when possible; bilastine should be avoided in patients with moderate to severe renal insufficiency who are receiving p-glycoprotein inhibitors.
Cladribine	BCRP/ABCG2 Inhibitors may increase the serum concentration of Cladribine. Management: Avoid concomitant use of BCRP inhibitors during the 4 to 5 day oral cladribine treatment cycles whenever possible. If combined, consider dose reduction of the BCRP inhibitor and separation in the timing of administration.
Colchicine	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Colchicine. Colchicine distribution into certain tissues (e.g., brain) may also be increased. Management: Colchicine is contraindicated in patients with impaired renal or hepatic function who are also receiving a p-glycoprotein inhibitor. In those with normal renal and hepatic function, reduce colchicine dose as directed. See full monograph for details.
Dabigatran Etexilate	P-glycoprotein/ABCB1 Inhibitors may increase serum concentrations of the active metabolite(s) of Dabigatran Etexilate. Management: Dabigatran dose reductions may be needed. Specific recommendations vary considerably according to US vs Canadian labeling, specific P-gp inhibitor, renal function, and indication for dabigatran treatment. Refer to full monograph or dabigatran labeling.
Dabrafenib	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Management: Seek alternatives to the CYP3A4 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects).
DOXOrubicin (Conventional	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of DOXOrubicin (Conventional). Management: Seek alternatives to P-glycoprotein inhibitors in patients treated with doxorubicin whenever possible. One U.S. manufacturer (Pfizer Inc.) recommends that these combinations be avoided.
Edoxaban	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Edoxaban. Management: See full monograph for details. Reduced doses are recommended for patients receiving edoxaban for venous thromboembolism in combination with certain P-gp inhibitors. Similar dose adjustment is not recommended for edoxaban use in atrial fibrillation.
Lefamulin	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Lefamulin. Management: Avoid concomitant use of lefamulin tablets with P-glycoprotein/ABCB1 inhibitors. If concomitant use is required, monitor for lefamulin adverse effects.
Lemborexant	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Lemborexant. Management: The maximum recommended dosage of lemborexant is 5 mg, no more than once per night, when coadministered with weak CYP3A4 inhibitors.
Lomitapide	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Lomitapide. Management: Patients on lomitapide 5 mg/day may continue that dose. Patients taking lomitapide 10 mg/day or more should decrease the lomitapide dose by half. The lomitapide dose may then be titrated up to a max adult dose of 30 mg/day.
Lorlatinib	May decrease the serum concentration of CYP3A4 Substrates (High risk with Inducers). Management: Avoid concurrent use of lorlatinib with any CYP3A4 substrates for which a minimal decrease in serum concentrations of the CYP3A4 substrate could lead to therapeutic failure and serious clinical consequences.
Stiripentol	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors). Management: Use of stiripentol with CYP3A4 substrates that are considered to have a narrow therapeutic index should be avoided due to the increased risk for adverse effects and toxicity. Any CYP3A4 substrate used with stiripentol requires closer monitoring.
Triazolam	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Triazolam. Management: Consider triazolam dose reduction in patients receiving concomitant weak CYP3A4 inhibitors.
Ubrogepant	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Ubrogepant. Management: In patients taking weak CYP3A4 inhibitors, the initial and second dose (if needed) of ubrogepant should be limited to 50 mg.
Venetoclax	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Venetoclax. Management: Consider a venetoclax dose reduction by at least 50% in patients requiring concomitant treatment with P-glycoprotein (P-gp) inhibitors.
Risk Factor X (Avoid combination)
Conivaptan	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
CYP3A4 Inducers (Strong)	May decrease the serum concentration of Lapatinib. Management: If therapy overlap cannot be avoided, consider titrating lapatinib gradually from 1,250 mg/day up to 4,500 mg/day (HER2 positive metastatic breast cancer) or 1,500 mg/day up to 5,500 mg/day (hormone receptor/HER2 positive breast cancer) as tolerated.
CYP3A4 Inhibitors (Strong)	May increase the serum concentration of Lapatinib. Management: If an overlap in therapy cannot be avoided, consider reducing lapatinib adult dose to 500 mg/day during, and within 1 week of completing, treatment with the strong CYP3A4 inhibitor.
DexAMETHasone (Systemic	May decrease the serum concentration of Lapatinib. Management: If therapy overlap cannot be avoided, consider titrating lapatinib gradually from 1,250 mg/day up to 4,500 mg/day (HER2 positive metastatic breast cancer) or 1,500 mg/day up to 5,500 mg/day (hormone receptor/HER2 positive breast cancer) as tolerated.
Fusidic Acid (Systemic)	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Grapefruit Juice	May increase the serum concentration of Lapatinib.
Idelalisib	May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors).
Lasmiditan	May increase the serum concentration of P-glycoprotein/ABCB1 Substrates.
PAZOPanib	Lapatinib may enhance the QTc-prolonging effect of PAZOPanib. Lapatinib may increase the serum concentration of PAZOPanib.
Pimozide	CYP3A4 Inhibitors (Weak) may increase the serum concentration of Pimozide.
St John's Wort	May decrease the serum concentration of Lapatinib. Management: If therapy overlap cannot be avoided, consider titrating lapatinib gradually from 1,250 mg/day up to 4,500 mg/day (HER2 positive metastatic breast cancer) or 1,500 mg/day up to 5,500 mg/day (hormone receptor/HER2 positive breast cancer) as tolerated.
Topotecan	BCRP/ABCG2 Inhibitors may increase the serum concentration of Topotecan.
Topotecan	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Topotecan.
VinCRIStine (Liposomal)	P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of VinCRIStine (Liposomal).

Monitoring parameters:

Tests and Things to Watch Out for While Taking Lapatinib:

Check heart function (LVEF) before starting and at times during treatment.
Get regular blood tests to check for white and red blood cells.
Regularly test the liver's health, especially certain enzymes and other markers, every 4-6 weeks.
Make sure the levels of minerals like calcium, potassium, and magnesium are okay.
Look out for signs of swelling or extra fluid in the body.
If there's a risk for a heart rhythm problem (QTc prolongation), get an ECG heart test.
Be aware of signs of lung problems like ILD or pneumonitis.
Watch for symptoms like diarrhea and skin reactions.

And for women who could become pregnant, it's essential to confirm if they're pregnant or not before starting Lapatinib.

How to administer Lapatinib (Tykerb)?

Take Lapatinib once every day.
Don't eat 1 hour before or 1 hour after taking it.
Always take it at the same time every day. Don't split the dose into smaller parts.

If Taking with Capecitabine:

Take capecitabine in two separate doses, roughly 12 hours apart.
Eat when you take capecitabine or within half an hour after having it.

Mechanism of action of Lapatinib (Tykerb):

Lapatinib is a drug that blocks two specific proteins called EGFR (ErbB1) and HER2 (ErbB2).
It does this by attaching itself to a part of the protein known as tyrosine kinase, stopping it from activating other parts inside the cell.
By doing this, it helps control the growth and life of cancer cells that have these proteins.
When used with hormone treatments, Lapatinib can help treat cancer that's become resistant to those treatments, especially if the cancer has both HER2+ and hormone receptors.

Basically, Lapatinib interferes with the signals that some cancer cells use to grow and survive.

Absorption:

Not all of the drug gets absorbed when taken, and the amount absorbed can vary.

Protein Binding:

Over 99% of Lapatinib binds to proteins in the blood, mainly to albumin and alpha-acid glycoprotein.

Metabolism:

The liver changes most of Lapatinib, mainly by enzymes called CYP3A4 and 3A5. Some other enzymes, CYP2C19 and 2C8, are involved but not as much.

How Long it Stays in the Body (Half-life):

It takes around 24 hours for half of the drug to leave the body.

Time to Highest Level in Blood:

About 4 hours after taking it, Lapatinib reaches its highest level in the blood.

How it Leaves the Body:

Most of Lapatinib leaves the body through feces (poop). In fact, 27% of the drug goes out unchanged this way (but it can vary between 3% and 67%). Very little (less than 2%) exits through urine (pee).

International Brands of Lapatinib: